Dust accumulation monitor

ABSTRACT

Dust accumulation monitors are provided to autonomously monitor dust accumulations. The dust accumulation monitors include a casing having a translucent portion, a light sensor configured to output a sensing signal based on sensed light penetrating through the translucent portion, a controller coupled to the light sensor to receive the sensing signal and configured to output a dust alert signal based on the received sensing signal, and a communication interface coupled to the controller and configured to output an alert based on the dust alert signal output by the controller. A dust accumulation monitoring system includes a plurality of dust accumulation monitors, and a central monitor communicatively connected to each of the plurality of dust accumulation monitors and configured to receive dust sensing signals from each of the plurality of dust accumulation monitors. The dust accumulation monitors may communicate through wired or wireless links with the central monitor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/554,357, filed Sep. 5, 2017, the disclosure of which is incorporatedby reference herein in its entirety.

TECHNICAL FIELD

The present subject matter relates to techniques and equipment tomonitor dust accumulation.

BACKGROUND

Accumulations of dust, including flammable and/or combustible dust, cantrigger dust explosions and other dangerous conditions. Accumulations offlammable dust commonly occur in process plants and other industrialenvironments, and monitoring of dust accumulations for prompt cleaningis therefore needed to maintain a safe work environment and preventdamage to facilities and machinery.

Dust explosions may be classified as being either primary or secondaryin nature. Primary dust explosions typically occur within individualpieces of equipment inside process plants or similar enclosures(baghouse, cyclone, grinder, etc.), and are generally controlled bypressure relief venting through purpose-built ducting to the atmosphere.Secondary dust explosions are the result of dust accumulations withinthe facility (e.g., outside of equipment) which occur when the dust isdisturbed, suspended, and ignited by the primary explosion, resulting ina more dangerous uncontrolled explosion inside the workplace. Facilitiesdamage and fatalities from dust explosions are normally the result ofsecondary dust explosions. Therefore, control of fugitive dust emissionsand housekeeping outside of equipment are a major focus of flammable orcombustible dust related standards and are the key to reducing thepotential for a catastrophic event.

Current National Fire Protection Association (NFPA) standards placesignificant emphasis on the need to maintain housekeeping of dustaccumulations outside of equipment to below some threshold thickness tominimize the associated risk. A common point of reference for invoking apotential hazard is when a dust accumulation is sufficiently thick toprevent the underlying surface color from being distinguished. This putsa significant demand on facility staff and resources in order toperiodically visually inspect elevated surfaces of a process facility,particularly if the process building volume is large, or buildingquantity is high (e.g., if the process facility includes multiplebuildings). Inspections may involve the use of man-lifts, cranes, and ateam of devoted personnel resulting in significant cost burden.

A need therefore exists for a system capable of efficiently andautomatically monitoring dust accumulations in a facility in order toenable maintaining of safe working conditions and efficient deploymentof housekeeping resources.

SUMMARY

The teachings herein alleviate one or more of the above noted problemsby providing a system capable of monitoring dust accumulations.

In accordance with the principles of the disclosure, a dust accumulationmonitor includes a casing, a light sensor, a controller, and acommunication interface. The casing has a translucent portion. The lightsensor is configured to output a sensing signal based on sensed lightpenetrating through the translucent portion. The controller is coupledto the light sensor to receive the sensing signal and is configured tooutput a dust alert signal based on the received sensing signal. Thecommunication interface is coupled to the controller and is configuredto output an alert based on the dust alert signal output by thecontroller.

The upper surface of the casing may be transparent.

The dust accumulation monitor may further include a light source coupledto the controller and configured to output light under control of thecontroller. The controller may be configured to sample the sensingsignal received from the light sensor while the light source isactivated to output light.

The light sensor and the light source may be disposed on opposite sidesof the translucent portion of the casing.

The light sensor may be disposed inside the casing and the light sourcemay be disposed outside of the casing.

Alternatively, the light sensor may be disposed outside the casing andthe light source may be disposed inside of the casing.

The dust accumulation monitor may further include a power source and atimer circuit configured to selectively provide power from the powersource to the controller on a periodic basis.

The communication interface may include at least one of a sound or lightemitter operative to emit an audible or visual alert based on the dustalert signal output by the controller.

The communication interface may include a communication transceiverconfigured to transmit a dust alert signal to a central monitor based onthe dust alert signal output by the controller.

The communication transceiver may include a wireless communicationtransceiver configured to wireless transmit the dust alert signal to thecentral monitor.

The communication transceiver may include a wired communicationtransceiver configured to transmit the dust alert signal to the centralmonitor.

The controller may store an adjustable reference level, and may beconfigured to output a dust alert signal based on a comparison of thereceived sending signal with the adjustable reference level.

The light sensor may include a Wheatstone bridge circuit.

In accordance with further principles of the disclosure, a dustaccumulation monitoring system may include a plurality of dustaccumulation monitors and a central monitor. The plurality of dustaccumulation monitors each include a light sensor configured to output adust sensing signal based on sensed light penetrating through atranslucent portion of the respective dust accumulation monitor. Thecentral monitor is communicatively connected to each of the plurality ofdust accumulation monitors and is configured to receive dust sensingsignals from each of the plurality of dust accumulation monitors.

The central monitor may be configured to selectively activate amachinery interlock based on the dust sensing signals received from eachof the plurality of dust accumulation monitors.

The central monitor may be configured to selectively activate an alertsystem based on the dust sensing signals received from each of theplurality of dust accumulation monitors.

The central monitor and the plurality of dust accumulation monitors maybe configured for wireless communication with each other.

Additional advantages and novel features will be set forth in part inthe description which follows, and in part will become apparent to thoseskilled in the art upon examination of the following and theaccompanying drawings or may be learned by production or operation ofthe examples. The advantages of the present teachings may be realizedand attained by practice or use of various aspects of the methodologies,instrumentalities and combinations set forth in the detailed examplesdiscussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accord withthe present teachings, by way of example only, not by way of limitation.In the figures, like reference numerals refer to the same or similarelements.

FIG. 1A shows an illustrative embodiment of an exemplary dustaccumulation monitor.

FIGS. 1B and 1C are functional block diagrams of exemplary dustaccumulation monitors.

FIGS. 2A and 2B are schematics of an exemplary light sensor circuit andan exemplary relay circuit as may be used in the dust accumulationmonitors shown in FIGS. 1A-1C.

FIGS. 3A and 3B are functional block diagrams of exemplary communicationinterfaces as may be used in the dust accumulation monitors shown inFIGS. 1A-1C.

FIGS. 4A, 4B, and 4C are functional block diagrams of exemplary powersources and a voltage regulator circuit as may be used in the dustaccumulation monitors shown in FIGS. 1A-1C.

FIG. 5 is functional block diagram of an exemplary timer circuit as maybe used in the dust accumulation monitors shown in FIGS. 1A-1C.

FIG. 6 is a simplified flow diagram outlining exemplary operation of adust accumulation monitor such as those shown in FIGS. 1A-1C.

FIG. 7 is a functional block diagram of an exemplary dust accumulationmonitoring system including dust accumulation monitors such as thoseshown in FIGS. 1A-1C.

FIGS. 8, 9, and 10 are plots showing experimental measurement resultsobtained using a dust accumulation sensor such as those shown in FIGS.1A-1C.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may be practiced without suchdetails. In other instances, well known methods, procedures, components,and/or circuitry have been described at a relatively high-level, withoutdetail, in order to avoid unnecessarily obscuring aspects of the presentteachings.

The various systems and methods described herein relate to themonitoring of dust accumulations. Such systems and methods may be used,for example, in monitoring of accumulations of dust including flammableor combustible particles and triggering of alerts in response to dustaccumulations exceeding an adjustable threshold.

In order to monitor dust accumulations, some embodiments of dustaccumulation monitors as described herein utilize a photocell resistors,such as photocell resistors used in dusk-to-dawn light sensors.Embodiments of the dust accumulation monitor are configured to provide atunable sensitivity of the photo cell. The dust accumulation monitorincludes a casing, for example an electrical enclosure, with atransparent cover. The photocell faces the transparent cover, and isused to detect when dust accumulation on the transparent cover issufficient to preclude light from passing through the transparent coverand reach the photocell. When the light detected by the photocell dropsbelow a threshold, the dust accumulation monitor determines that thehazard criteria has been achieved and activates an alert system.

The dust accumulation monitor provides an adjustable or tunablesensitivity to thereby cause activation of the alert system at anadjustable dust accumulation threshold or dust accumulation thickness.The ability to change the sensitivity allows the device to detectvarious thicknesses of dust to a maximum limiting thickness value. Inaddition, the sensitivity feature allows the sensor to be located invery bright or dark locations, with the sensitivity calibratedappropriately to reduce potential false positive alarms. The adjustablesensitivity also enables the sensitivity to be adjusted depending on thetype of dust being detected, since a higher density dust may impedelight transmission at a lower thickness than lower density dusts.

In some chosen device locations (e.g., rafters), the ambient light maybe very low, thus reducing the range of the sensor's capability. Inother locations, ambient light may be highly variable therebyintroducing uncertainty in the relationship between dust accumulationand light sensed by the photocell. In such cases, a devoted light source(e.g., an external light source) may be integrated in the dustaccumulation monitor and used to provide sufficient sensitivity rangefor the sensor to minimize false positive alarms.

The photocell of the dust accumulation monitor provides an outputsignal, also referred to as a sensing signal, that qualifies the dustaccumulation thickness at a particular location at which the dustaccumulation monitor is located. In some examples, the dust accumulationmonitor may additionally or alternatively quantify the dustaccumulation. In general, however, the monitor is intended to generateand emit a signal when a dust accumulation sufficient to inhibit lighttransmission has been deposited on the monitor, which may correspond toa dust accumulation sufficient to obscure an underlying surface color.Based on the generated/emitted alert signal, an operator can theninspect the location to confirm the presence of dust accumulation anddetermine what action(s) to take (e.g., clean dust, reset device, or thelike). The monitor thereby provides a method for remotely monitoring thedust accumulation rate in order to optimize cleaning frequency withouthaving to continuously inspect the location. Remote and independentoperation of the monitor relieves the burden of utilizing resources toinspect (often unnecessarily) elevated surfaces to determine dustaccumulation rates.

Reference is now made in detail to the examples illustrated in theaccompanying drawings and discussed below.

FIG. 1A shows an illustrative embodiment of a dust accumulation monitor100 that may be used for monitoring dust accumulations. The dustaccumulation monitor 100 has a casing 101, such as a solid box, withinwhich components of the dust accumulation monitor 100 are mounted. Thecasing 101 includes a translucent portion 101 a which may be translucentor transparent. In general, the dust accumulation monitor 100 isdesigned to be oriented such that the translucent portion 101 a facesupwards with respect to gravity. Additionally, a light sensor 103 of thedust accumulation monitor 100 is disposed so as to sense light passingthrough the translucent portion 101 a. As such, the light sensor 103 isgenerally disposed such that a light sensing or light receiving portionthereof faces (e.g., is oriented towards) the translucent portion 101 a,as shown in FIG. 1A.

FIG. 1B shows a functional block diagram of an example of the dustaccumulation monitor 100. The dust accumulation monitor 100 includes thelight sensor 103 such as a photocell disposed within the casing 101 anddisposed so as to sense light passing through the translucent portion101 a of the casing 101. Additionally, the light sensor 103 iscommunicatively connected to a controller 105, and is configured tooutput a sensing signal to the controller 105 based on sensing lightpenetrating through the translucent portion 101 a. The controller 105 iscommunicatively coupled to the light sensor 103 to receive the sensingsignal, and is configured to output a dust alert signal based on thereceived sensing signal. For example, the controller 105 may process thereceived sensing signal in order to estimate a current thickness of dustaccumulation on the translucent portion 101 a, and may output the dustalert signal when the estimated thickness exceeds a threshold value(e.g., or when the sensed light falls below a light threshold value).

The controller 105 may be a microcontroller that can be used, in someembodiments, to compare a voltage sensing signal received from the lightsensor 103 to a programmed reference threshold, and to trigger an alertbased on the result of the comparison. The controller 105 may be anopen-source microcontroller, may operate at low voltage (e.g., 6 volts),may include both analog and digital input pins, and may operate with lowpower consumption (e.g., 19 mA of current consumption, or as low as 12mA).

The dust accumulation monitor 100 further includes a communicationinterface 107 communicatively coupled to the controller 105 andconfigured to output an alert based on the dust alert signal output bythe controller 105. For example, the communication interface 107 maytake the form of a strobe light 108 or other visual indicator configuredto output a visual alert, a speaker or other auditory output meansconfigured to output an auditory alert, or a wired or wirelesstransceiver configured to transmit a signal to a central monitor remotefrom the dust accumulation monitor 100.

In some embodiments, the dust accumulation monitor 100 further includesa light source 113, which may be internal or external. The use of thelight source 113 reduces the effect of variable ambient light variationson the dust accumulation monitor 100, and enables operation of themonitor 100 in dark locations. The light source 113 is disposed on anopposite side of the translucent portion 101 a relative to the lightsensor 103. As such, the light source 113 may be disposed outside of thecasing 101 in an embodiment in which the light sensor 103 is mountedinside of the casing 101 (see, e.g., FIG. 1B) or the light source 113may be mounted inside of the casing 101 in an embodiment of the dustaccumulation monitor 100 a in which the light sensor 103 is disposedoutside of the casing 101 (see, e.g., FIG. 1C). The light source 113 iscommunicatively coupled to the controller 105 and is configured tooutput light under control of the controller 105. For example, thecontroller 105 may activate the light source 113 immediately prior toand during a dust accumulation reading so as to sample the sensingsignal received from the light sensor 103 while the light source 113 isactivated and outputting light. The light source 113 may include one ormore light emitting diodes (LEDs) or other light emitters.

The dust accumulation monitor 100 can further include a power source 109for providing electrical power to components of the dust accumulationmonitor 100 for its operation, including to the light sensor 103, thecontroller 105, the communication interface 107, and the optional lightsource 113. An optional timer circuit 111 may be used to reduce powerconsumption of the dust accumulation monitor 100, as discussed in moredetail below.

The light sensor 103 can include one or more photo sensors, photocells,or other sensors that allow for the detection of light. Photo sensors orphotocells are small, inexpensive, and low-power sensors having anextended useful life, and may include cadmium-sulfide (CdS) cells,light-dependent resistors (LDR), and photoresistors, among others. Inoperation, photo sensors or photocells may function as resistors havinga resistance value that changes depending on an amount or intensity oflight that impinges or shines onto a sensing face of the photocell.

FIG. 2A shows an illustrative light sensor circuit that may be used aspart of the light sensor 103. As shown in the figure, the light sensorcircuit can include a Wheatstone bridge circuit including a photo sensorand three resistors (or, more generally, impedance elements). The lightsensor circuit can include two power terminals In+ and In− at whichoperating power V_(In) is applied, a first series interconnection ofresistors R₁ and R₂ coupled between the power terminals In+ and In−, anda second series interconnection of a resistor R₃ and the photo sensorcoupled between the power terminals In+ and In−.

In the light sensor circuit of FIG. 2A, the output signal V_(Out) isgiven by:

${V_{Out} = {( {\frac{R_{PS}}{R_{3} + R_{PS}} - \frac{R_{2}}{R_{1} + R_{2}}} )*V_{In}}},$

where R_(PS) is the resistance of the photo sensor.

In operation, the output voltage V_(Out) varies as the resistance R_(PS)of the photo sensor changes, and thereby varies as the amount of lightimpinging on the light sensor 103 varies. In particular, V_(Out) has arelatively low value when a lot of light impinges on the light sensor103 (e.g., when no dust is present) such that the light sensor 103 haslow resistance, and V_(Out) increases to a relatively high value aslight impinging on the light sensor 103 decreases (e.g., as lighttransmission decreases with increased dust thickness) such that thelight sensor 103 has high resistance.

The controller 105 may selectively provide the operating power V_(In) tothe light sensor circuit at the terminals In+ and In−. For example, anoutput pin of the controller 105 may be coupled to the terminal In+, andmay selectively provide operating power to the terminal In+, while theterminal In− may be connected to a ground node or ground potential.

Alternatively, a relay circuit such as that shown in FIG. 2B can be usedto selectively provide the operating power V_(In) to the light sensorcircuit under control of the controller 105. For example, the relaycircuit may be used in situations in which the light sensor circuit isprovided with higher power (e.g., higher current) than can be output bythe controller 105. As shown in FIG. 2B, the controller 105 controls arelay such as a photo-relay to cause the relay to selectively close.When the relay is open, no operating power is provided to the lightsensor circuit; however, when the relay is closed under control of thecontroller 105, the sensor power source provides the operating power tothe light sensor circuit for operation of the light sensor circuit. Thesensor power source may correspond to the same power source 109 used inoperation of the dust accumulation monitor 100, or may be a power sourcehaving a higher current or voltage than that provided by the powersource 109.

While the light sensor circuit receives operating power, the lightsensor circuit produces a sensing signal (e.g., V_(Out)) across itsoutput terminals. The sensing signal V_(Out) varies based on the amountor intensity of light impingent on the photo sensor, and can therebyvary based on the amount of sensed light penetrating through thetranslucent portion 101 a of the dust accumulation monitor 100. Ingeneral, the output terminal(s) V_(Out) of the light sensor circuit arecommunicatively coupled to input terminals of the controller 105 toenable the controller 105 to receive the sensing signal output by thelight sensor 103 or light sensor circuit.

The controller 105 performs processing based on the sensing signal ofthe light sensor 103 to estimate a dust accumulation thickness on thetranslucent portion 101 a of the dust accumulation monitor 100. Inoperation, the controller 105 may sample the sensing signal receivedfrom the light sensor 103, for example during a period of time when thelight source 103 is activated and outputting light. The controller 105may compare the sampled sensing signal value to a predeterminedthreshold value and output a dust alert signal based on the comparison.

In one example in which the sensing signal value increases as less lightimpinges on the light sensor 103, the controller 105 determines whetherthe sampled sensing signal value exceeds the predetermined thresholdvalue and triggers output of the dust alert signal when the sampledsensing signal value exceeds the predetermined threshold value. Inanother example in which the sensing signal value decreases as lesslight impinges on the light sensor 103 (e.g., if V_(Out) has a reversepolarity relative to the one example), the controller 105 determineswhether the sampled sensing signal value falls below the predeterminedthreshold value and triggers output of the dust alert signal when thesampled sensing signal value falls below the predetermined thresholdvalue.

Based on the processing, the controller 105 outputs a dust alert signalto the communication interface 107 to cause the communication interface107 to issue an audible alert, a visual alert, and/or a communication toa central monitor.

FIGS. 3A and 3B show simplified block diagrams of two illustrativecommunication interfaces 107. The communication interface 107 caninclude a sound or light emitter, such as a strobe or other light, aspeaker or alarm, or other device operative to output an audible and/orvisual alert. In this way, the communication interface 107 can emit anaudible or visual alert based on the dust alert signal output by thecontroller 105. In general, a high efficiency strobe light can be usedto enable the strobe to continue operation for four days from a singlebattery charge. Additionally or alternatively, the communicationinterface can include one or more transceivers, such as a firstcommunication interface 107 a that includes a wireless transceiver andan antenna or a second communication interface 107 b that includes awired transceiver. The first and second communication interfaces 107 aand 107 b can transmit the dust alert signal to a central monitor basedon the dust alert signal output by the controller 105. The first andsecond communication interfaces 107 a and 107 b can additionallytransmit to the central monitor other information including a lowbattery signal, a periodic status report, or the like, under the controlof the controller 105.

In some embodiments, the transceiver-based communication interfaces(e.g., 107 a, 107 b) are configured for two-way communication. Thecommunication interfaces 107 a can then transmit the dust alert signalto the central monitor, and can additionally receive control commandsfrom the central monitor and forward the commands to the controller 105.For example, the central monitor can transmit a command to perform oneor more dust accumulation measurements via the communication interfaces107 a, 107 b, and the controller 105 may then perform the measurementsin response to receiving the command.

FIGS. 4A and 4B show simplified block diagrams of two illustrative powersources 109. As shown, the power source 109 can include one or both of abattery-based power source 109 a and a power-line power source 109 b.The battery-based power source 109 a includes a battery (e.g., a lithiumor alkaline battery) and an optional power regulator or power converterin line with the battery output to provide regulated power at a desiredpower level for operation of the dust accumulation monitor 100. Thepower-line power source 109 b can include a power converter and avoltage regulator to convert line voltage (received at an input) to thedesired power level for operation of the dust accumulation monitor 100.Note that a hybrid power source (not shown) may include elements of boththe battery-based power source 109 a and the power-line power source 109b to enable operation of the dust accumulation monitor 100 on linevoltage while providing for a battery-backup as needed. FIG. 4C shows anillustrative voltage regulator circuit that may be used in the powersource 109. Note that in some embodiments, all components of the dustaccumulation monitor 100 may operate at a same voltage level output bythe power source 109. In other embodiments, the power source 109 may beconfigured to output two different power levels, for example to includea lower power level for powering the controller 105 and communicationinterface 107 and a higher power level for powering the light sensor 103and light source 113 via relays (see, e.g., FIG. 2B).

In order to lower the power expenditure of the dust accumulation monitor100, the dust accumulation monitor 100 can include the timer circuit 111configured to selectively provide power from the power source 109 to thecontroller 105 and other components of the dust accumulation monitor100. For example, the timer circuit 111 can provide power on a periodicbasis, so as to reduce the amount of power consumed by the components ofthe monitor 100 during standby operation. Standby operation maycorrespond to a lower power operating mode in which the dustaccumulation monitor 100 operates when no dust accumulation measurementsare being taken, and during which the controller 105, light sensor 103,and other components can be powered off to reduce energy expenditure. Inone implementation, a battery-powered dust accumulation monitor 100 canoperate independently for up to twelve months without requiring chargingor battery replacement. In other embodiments battery-powered dustaccumulation monitor 100 can operate independently for longer periods oftime (e.g., maintain operation for over one year, or multiple years, ona single battery charge) through selective cycling of sensors andcomponents as discussed below in relation to FIG. 5.

FIG. 5 shows a simplified block diagram of an illustrative timer circuit111 receiving an input power supply voltage V_(DD) _(_) _(IN) (e.g.,from the power source 109) and selectively providing the input powersupply voltage to the output V_(DD) _(_) _(OUT) (e.g., to the controller105 and other components of the dust accumulation monitor 100). Thetimer circuit 111 includes a timer 501 that is powered by the inputpower supply voltage and that selectively closes a switch 503 (e.g., aMOSFET switch) to provide the input power to the output V_(DD) _(_)_(OUT).

The timer 501 is operative to close the switch 503 on a periodic basis.The period can be adjusted according to the value of the resistorR_(EXT), and can for example be adjusted in a range of milliseconds toone day (e.g., in the range of 30 minutes to 12 hours in someembodiments). Every time the period has elapsed, the timer 501 closesthe switch 503 in order to provide the input power supply voltage V_(DD)_(_) _(IN) to the output V_(DD) _(_) _(OUT). In general, the timer 501continues to provide the input power to the output V_(DD) _(_) _(OUT)until receiving a power-off signal from the controller 105 at its DONEinput. Alternatively or additionally, the timer 501 can continue toprovide the input power to the output V_(DD) _(_) _(OUT) for apredetermined amount of time, and may automatically open the switch 503once the predetermined amount of time has elapsed.

FIG. 6 is a simplified flow diagram outlining operation of the dustaccumulation monitor 100 according to some embodiments. The operationbegins at step 601 with the dust accumulation monitor being activated orturned on. The activation may result in the timer circuit 111 beingpowered on and beginning operation.

In step 603, the timer circuit 111 monitors the time interval or periodfor periodically closing switch 503 and providing input power to othercomponents of the dust accumulation monitor 100. The timer circuit 111monitors the time interval to determine whether the time interval haselapsed (step 605), and remains in the monitoring status until the timeinterval has elapsed. Once the time interval has elapsed, operationproceeds in step 607 with the timer circuit 111 providing operatingpower to the controller 105, the optional light source 113, and othercomponents of the dust accumulation monitor including the light sensor103 and the communication interface 107 so as to turn on thosecomponents.

While the controller 105 and optional light source 113 are powered on,the controller 105 proceeds to monitor its input terminals for thesensing signal output by the light sensor 103 in step 609. For example,the controller 105 may monitor an analog or digital signal at its input,and may sample the signal and process the signal sample to determinewhether a dust alert signal should be output (step 611). In this regard,the controller 105 may compare an analog sensing signal from the lightsensor 103 to a predetermined threshold level, and may thereby determinethat the predetermined dust thickness has been reached if the sensingsignal exceeds the threshold. The controller 105 may digitize thesensing signal from the light sensor 103 into a digital sensing signal(e.g., using an analog-to-digital converter) and may compare the digitalsensing signal to a predetermined threshold level, and may therebydetermine that the predetermined dust thickness has been reached if thedigital sensing signal exceeds the threshold.

If the controller 105 determines that the threshold dust level isreached (step 611, Yes), the controller 105 proceeds to generate a dustalert signal to the communication interface 107 to issue an auditory orvisual alert and/or to notify the central monitor (step 613). Thecontroller 105 then causes the dust accumulation monitor 100 to enter alow power mode. Alternatively, if the controller 105 determines that thethreshold dust level is not reached (step 611, No), the controller 105causes the timer 501 to turn off power to the controller 105, optionallight source 113, and other components of the dust accumulation monitor100 and to resume monitoring of the time interval (step 603).

In accordance with the various embodiments outlined herein, the dustaccumulation monitor 100 can function as a standalone device monitoringa local accumulation of dust. In this regard, each dust accumulationmonitor 100 is self-contained and provides a local audible and/or visualalarm when an accumulation threshold or other condition is satisfied. Ingeneral, such dust accumulation monitors 100 may be self-powered devicesthat operate based on battery power, solar power, or the like, thoughsuch devices may also rely on line power for operation.

Additionally, the dust accumulation monitor 100 can function as anetworked device that forms part of a network of devices monitoringaccumulations of dust at multiple locations (e.g., throughout afacility). In the networked embodiment, which is illustratively shown inFIG. 7, a dust monitoring system 700 can include multiple (e.g., ‘n’)dust accumulation monitors 100 that are each configured to send a dustalert signal to a central monitor 701 when a dust accumulation isdetected. In turn, the central monitor 701 may provide audible and/orvisual alarms in addition to or instead of alerts or alarms activated inthe individual dust accumulation monitors 100. The central monitor 701may additionally or alternatively provide an alert system 705 such as analarm system configured to cause evacuation of a facility, notifyemergency crews, or the like.

The central monitor 701 may also be configured to activate systeminterlocks or machinery interlocks 703, for example to halt operation ofmachinery that may trigger a dust explosion and/or that may produceadditional dust. Machinery operation may be halted until the dustaccumulation condition is rectified, for example by removing the dustaccumulation and/or initiating a reset of the central monitor 701 anddust accumulation monitors 100. In this approach, wireless communicationcapabilities may be integrated into individual dust accumulationmonitors 100 to provide the ability to send remote notifications to thecentral monitor 701 and to relay notifications between the dustaccumulation monitors 100 and the central monitor 701.

The dust monitoring system 700 and components thereof may be powered bya continuous hard-wired 12V power supply (e.g., in cases in which dustaccumulation monitors 100 form a wired network with the central monitor701 and receive power over Ethernet) or by batteries, solar cells, orother power sources.

FIGS. 8-10 show plots of experimental measurements from a dustaccumulation sensor 100 in accordance with the principles of thedisclosure. FIG. 8 is a plot of the sensing signal voltage amplitude(y-axis) for different thicknesses of fine wood dust (range: 0 to 0.41inch) under two ambient lighting conditions: a first condition in whichambient lighting was present, and a second ‘dark’ condition in which noambient lighting was present. As shown, the sensing signal voltageamplitude increases with the fine wood dust accumulation thickness.

FIG. 9 is a plot of the sensing signal voltage amplitude (y-axis) fordifferent thicknesses of fine wood dust (range: 0 to 0.41 inch) undervarious lighting conditions: a first condition in which only overheadlighting was used, a second condition in which both overhead lightingand a light source 113 were used, a third condition in which only thelight source 113 was used (without ambient or overhead lighting), and afourth condition in which no light source and no overhead lighting wereused. As shown, the sensing signal voltage amplitude increases with thefine wood dust accumulation thickness.

FIG. 10 is a plot of the sensing signal voltage amplitude (y-axis) fordifferent thicknesses of different types of dust particles, includingpolystyrene (thickness range 0 to 0.54 inch), fine wood dust (thicknessrange: 0 to 0.41 inch), and lycopodium powder (thickness range 0 to 0.9inch). In accordance with the findings in FIG. 10, different types ofdust have different characteristics, for example finer dust material(e.g., lycopodium powder) block light at thinner relative thicknesses,and translucent materials (e.g., polystyrene) block less light even atthicker relative thicknesses. In order to activate an alert, the dustaccumulation monitor 100 can thus be adjusted or calibrated based on atype of dust expected to accumulate and based on a thickness at whichthe alert signal should be activated for the type of dust by adjustingthe predetermined voltage threshold at which the alert signal isactivated by the controller 105.

As noted above in relation to FIG. 10, the dust accumulation monitor(100) can be calibrated (or re-calibrated) based on different types ofdust materials (e.g., to account for dust particle size, opacity, or thelike). Additionally, as illustrated in FIGS. 8 and 9, the dustaccumulation monitor (100) can be calibrated (or re-calibrated) based ondifferent light levels in order to increase or decrease sensitivity. Inthis way, the dust accumulation monitor 100 can provide approximatethickness measurement estimates for different materials and adjustsensitivity threshold for activating the alarm/strobe according to amaterial type (e.g., to increase sensitivity for materials with higherflammability).

The dust accumulation monitor 100 may also activate the alert signal(e.g., activate a strobe light, or issue an alert via a transceiver) inthe event of detecting an internal component failure, a low battery, orthe like.

Various enclosure designs, casings, and packaging can be used based onapplications (and space constraints), and for ease of manufacturing.Optionally, the design can provide wireless communication capabilitiesto communicate dust measurements and/or alert activation to a centralmonitoring station.

As shown by the above discussion, functions relating to the monitoringof dust accumulations may be implemented on controllers connected fordata communication via transceivers. The controllers may include acentral processor or other processing device, and memory or storagemedia (RAM, ROM, EEPROM, cache memory, disk drives etc.) for code anddata storage. Software functionalities may involve programming,including executable code as well as associated stored data, e.g. filesused for setting the threshold used for triggering the alert signal. Thesoftware code is executable by the general-purpose processor of thecontroller. Execution of such code by a processor enables the dustaccumulation monitor 100 to implement the methodology for monitoringdust accumulation in essentially the manner performed in theimplementations discussed and illustrated herein.

Unless otherwise stated, all measurements, values, ratings, positions,magnitudes, sizes, and other specifications that are set forth in thisspecification, including in the claims that follow, are approximate, notexact. They are intended to have a reasonable range that is consistentwith the functions to which they relate and with what is customary inthe art to which they pertain.

The scope of protection is limited solely by the claims that now follow.That scope is intended and should be interpreted to be as broad as isconsistent with the ordinary meaning of the language that is used in theclaims when interpreted in light of this specification and theprosecution history that follows and to encompass all structural andfunctional equivalents.

Except as stated immediately above, nothing that has been stated orillustrated is intended or should be interpreted to cause a dedicationof any component, step, feature, object, benefit, advantage, orequivalent to the public, regardless of whether it is or is not recitedin the claims.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”or any other variation thereof, are intended to cover a non-exclusiveinclusion, such that a process, method, article, or apparatus thatcomprises a list of elements does not include only those elements butmay include other elements not expressly listed or inherent to suchprocess, method, article, or apparatus. An element proceeded by “a” or“an” does not, without further constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises the element.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

What is claimed is:
 1. A dust accumulation monitor comprising: a casinghaving a translucent portion; a light sensor configured to output asensing signal based on sensed light penetrating through the translucentportion; a controller coupled to the light sensor to receive the sensingsignal and configured to output a dust alert signal based on thereceived sensing signal; and a communication interface coupled to thecontroller and configured to output an alert based on the dust alertsignal output by the controller.
 2. The dust accumulation monitor ofclaim 1, wherein the upper surface of the casing is transparent.
 3. Thedust accumulation monitor of claim 1, further comprising: a light sourcecoupled to the controller and configured to output light under controlof the controller, wherein the controller is configured to sample thesensing signal received from the light sensor while the light source isactivated to output light.
 4. The dust accumulation monitor of claim 3,wherein the light sensor and the light source are disposed on oppositesides of the translucent portion of the casing.
 5. The dust accumulationmonitor of claim 4, wherein the light sensor is disposed inside thecasing and the light source is disposed outside of the casing.
 6. Thedust accumulation monitor of claim 4, wherein the light sensor isdisposed outside the casing and the light source is disposed inside ofthe casing.
 7. The dust accumulation monitor of claim 1, furthercomprising: a power source; and a timer circuit configured toselectively provide power from the power source to the controller on aperiodic basis.
 8. The dust accumulation monitor of claim 1, wherein thecommunication interface comprises at least one of a sound or lightemitter operative to emit an audible or visual alert based on the dustalert signal output by the controller.
 9. The dust accumulation monitorof claim 1, wherein the communication interface comprises acommunication transceiver configured to transmit a dust alert signal toa central monitor based on the dust alert signal output by thecontroller.
 10. The dust accumulation monitor of claim 9, wherein thecommunication transceiver comprises a wireless communication transceiverconfigured to wireless transmit the dust alert signal to the centralmonitor.
 11. The dust accumulation monitor of claim 9, wherein thecommunication transceiver comprises a wired communication transceiverconfigured to transmit the dust alert signal to the central monitor. 12.The dust accumulation monitor of claim 1, wherein the controller storesan adjustable reference level, and is configured to output a dust alertsignal based on a comparison of the received sending signal with theadjustable reference level.
 13. The dust accumulation monitor of claim1, wherein the light sensor comprises a Wheatstone bridge circuit.
 14. Adust accumulation monitoring system comprising: a plurality of dustaccumulation monitors, each comprising a light sensor configured tooutput a dust sensing signal based on sensed light penetrating through atranslucent portion of the respective dust accumulation monitor; and acentral monitor communicatively connected to each of the plurality ofdust accumulation monitors and configured to receive dust sensingsignals from each of the plurality of dust accumulation monitors. 15.The dust accumulation monitoring system of claim 14, wherein the centralmonitor is configured to selectively activate a machinery interlockbased on the dust sensing signals received from each of the plurality ofdust accumulation monitors.
 16. The dust accumulation monitoring systemof claim 14, wherein the central monitor is configured to selectivelyactivate an alert system based on the dust sensing signals received fromeach of the plurality of dust accumulation monitors.
 17. The dustaccumulation monitoring system of claim 14, wherein the central monitorand the plurality of dust accumulation monitors are configured forwireless communication with each other.